1. Field of the Invention
Honeycomb structures are generally made either by assembling corrugated parts or by expanding a stack of flat sheets that have been adhered together in particular configurations. In the past, heavy honeycomb structures have been made using the corrugated parts because of the greater forces that are required to expand heavy or thick flat sheets into honeycomb structures. This invention relates to heavy honeycomb structures made by expanding a stack of flat sheets.
2. Description of Related Art
U.S. Pat. No. 3,493,450, issued Feb. 3, 1970 on the application of D. G. Judge, discloses a comparison of corrugated and expanded honeycomb manufacture and describes a process of expanded honeycomb manufacture in detail.
U.S. Pat. No. 3,184,365, issued May 18, 1965 on the application of E. L. Rule, discloses a process and apparatus for printing, cutting, and stacking in exact registry, identical sheets of collapsed honeycomb laminate.
U.S. Pat. Nos. 5,670,001 and 5,792,295, issued Sep. 23, 1997 and Aug. 11, 1998 on the applications of F. Huebner et al., disclose processes and apparatuses for making collapsed honeycomb that is easier to expand by avoidance of early impregnation of the honeycomb layers.
This invention relates to a honeycomb structure having a multitude of collapsed honeycomb cells with each cell having six cell walls of substantially equal cell wall length and each cell wall comprising at least two layers of sheet material wherein the sheet material of all of the layers of two opposite walls of each cell are bonded to each other and to walls of other cells and none of the layers of the remaining four walls of each cell are adhered together or to walls of other cells. It also relates to a process for making such a honeycomb structure comprising the steps of: (a) applying lines of bonding agent to one layer of sheet material such that the lines are parallel with a finished structure length of one cell wall length and are spaced apart with a finished structure length of one cell wall length between lines of bonding agent; (b) placing a layer of sheet material on the sheet material of step (a); (c) applying lines of bonding agent to the layer of step (b) such that the lines are parallel with a finished structure length of one cell wall length, are spaced apart with a finished structure length of three cell wall lengths between lines of bonding agent, and are located directly coincident with lines of bonding agent on the sheet material of step (a); (d) placing a layer of sheet material on the sheet material of step (c); (e) applying lines of bonding agent to the layer of step (d) such that the lines are parallel with a finished structure length of one cell wall length, are spaced apart with a finished structure length of one cell wall length between lines of bonding agent, and, at least some, are located directly coincident with lines of bonding agent on the sheet material of step (c).